请高手指教，谢谢~~~

yanchunqing2010

想请教下，最后一句为什么是与0x3F取反相与。此例程是USB_HOST_MSC例程下， cppidma.c下面的函数，请高手指教，谢谢~~~
#define DESC_REGION_SIZE                    (1024 * 20) + SOC_CACHELINE_SIZE_MAX
unsigned int region0DescriptorSpace[DESC_REGION_SIZE];

/*Queue region setup */
    /*The Descriptor region address is aligned for SOC_CACHELINE_SIZE_MAX Byte access */
    descAddress = (unsigned int)region0DescriptorSpace;
    /*Add SOC_CACHELINE_SIZE_MAX to the starting address */
    descAddress = descAddress + BYTE_ALIGNMENT;
    /*Align the strating adress */
    descAddress &= ~0x3F;

human

该地址要求64位边界对齐